1. Field of the Invention
The present invention relates to a level detector which is configured to analyze a light receiving position of laser light received by a light receiving unit. Priority is claimed to Japan Pat. App. No. 2005-304307, filed Oct. 19, 2005, hereby incorporated by reference.
2. Description of the Related Art
In general, a distance measurement device or a level detector which is configured such that: for measuring a distance from a position to another position, or a level to another position, etc., for example, laser light for the measurement is emitted from the position toward another position, and the laser light is received by a light receiving unit provided at the another position, is well-known. Conventionally, JP-A-2004-309440 discloses a level detector configured such that a plurality of light receiving elements are arranged in parallel up and down to form a light receiving element unit, a light receiving position of laser light received by the light receiving element unit is obtained based on a light receiving signal of the light receiving element.
The level detector according to JP-A-2004-309440 includes: a plurality of amplifiers configured to amplify the light receiving signals output from each light receiving element respectively; a plurality of comparators configured to compare signals output from each amplifier with thresholds respectively; and a microprocessor configured to detect a center position of the laser beam received by the light receiving element unit, based on compared signals output from each comparator.
In such a level detector, it is necessary to provide amplifier and comparator for each light receiving element, therefore there are problems that the circuit is complex and the detector is of expensiveness.
Therefore, a level detector is proposed comprising: a first amplifier circuit configured to amplify a light receiving signal output from one terminal of a light receiving element unit; a first peak hold circuit configured to hold a peak value of the light receiving signal output from the first amplifier circuit; a second amplifier circuit configured to amplify a light receiving signal output from another terminal of the light receiving element unit; a second peak hold circuit configured to hold a peak value of the light receiving signal output from the second amplifier circuit; and an arithmetic control device configured to detect a light receiving position of laser light received by the light receiving element unit from the peak values held in the first and the second peak hold circuits.